Early Construction Practice Before 1830 1833 1860 1880
Early Christchurch Both stone and clay brick masonryVictorian Christchurch in 1885 (Coxhead 1885) Christchurch’s first ‘skyscraper’, photo circa 1910 (Brittenden Collection 1910)
1931 Hawke’s Bay earthquake (256 deaths, 525 aftershocks in 14 days, M7.8)Hastings Street, Napier, circa 1914 (Alexander View down Hastings Street, Napier after the Turnbull Library). 1931 earthquake (Alexander Turnbull Library).
1931 Hawke’s Bay earthquake (earthquake followed by fire)Looking over Napier at the buildings ruined by Ruins of the Napier Anglican Cathedralthe 1931 earthquake and the fires (Alexander after the 1931 Napier earthquake Turnbull Library). (Alexander Turnbull Library).
Slow steady loss of heritage unreinforced masonry buildings, post-1930Alexander Turnbull Library Alexander Turnbull Library Wellington, 1950
Concrete Masonry Construction flourishes, 1960-1990 1965 Warren Townhouse
1975 Dawn of Capacity Design• Ductility• Confinement• Plastic hinges
Earthquake statistics• Date: 04.09.2010 4:35 am (NZ Standard time)• Magnitude: Mw 7.1• Focal depth: 10 km• Maximum Intensity: MMI 8• No direct fatalities (one heart attack)• 1 major casualty due to falling chimney• Largest earthquake on record to occur within 40 km of major city and cause no fatalities Credit: GeoNet
Fault trace• Numerous places where offset could be measured – right lateral up to about 3 m, with variable vertical throw (mostly < 1 m). Credit: GNS
22 February 2011• David Biggs overnighted in Grand Chancellor hotel• Jason flew from Nelson arriving 7.30 am, bags checked on to Wellington• Interviewed by Canterbury TV at 11.00 am• Ken Elwood (Vancouver) in audience• 84 attendees at afternoon seminar• Earthquake struck at 12.51 pm
Command centre Day 5 Cathedral Day 4 During earthquake
Transect• Designed to sample on a pre-determined route• Used for sampling biological species• Deficiencies – Dependent on route, and route was intentionally selected to survey large stock of URM buildings – Level 1 sampling, building condition judged exclusively by appearance of street frontage – Data is subjective
URM = 52%Of URM, 48% redRed URM = 24.8%Some buildings worsethan appear from streetfrontSay about 1 in 3 redoverallThanks to Quincy Ma,Liam Wotherspoon,Rick Henry
Benefits• Immediately of interest to Christchurch City Council• Requested by the Historic Places Trust• Used to provide accurate information to media• Used in response to a request to identify a suite of ‘indicator buildings’
Indicator buildings• If these buildings exhibit damage then others of this class need to be inspected also• URM: Soft enough (damaged) so that it did not take shock of comparable intensity to cause further damage• Other forms: Exhibiting measurable damage that can be easily monitored
David was one of the last paying customers! Grand Chancellor Hotel • 1980s construction • Constructed in 2 stages • Core wall up to 7th storey • Perimeter moment frame above • South face dropped 600mm to 900mm due to failure of wall at ground level and columns at 7th storey
RC Structural Wall Buildings Overall differential settlement of around 300 mmLightly confined boundary zones
Other locations being inspected 1000+ clay brick masonry 500+ concrete masonry 100+ stone masonry 250+ churches Perhaps 25% of all heritage masonry buildings in New Zealand
Is this what we should expect for an earthquake this intense? (1:10,000 years or 1:3.65 million days!) CENTRAL CITY AND NZS1170 SPECTRA CLASS D DEEP OR SOFT SOIL Larger Horizontal Components 1.8 1.6 NZS1170 2500-yr Class D 1.4Demand 1.2 NZS1170 500-yr Class D Deep or Soft Soil CHHC_MaxH_FEB 1 SA(T) (g) 0.8 CCCC_MaxH_FEB 0.6 CBGS_MaxH_FEB 0.4Capacity REHS_MaxH_FEB 0.2 GM_Larger_FEB 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Period T(s)
Is this what we should expect?• Yes. URM buildings consistently collapse in large earthquakes• The NZ URM building stock is analogous to that of other European colonies. Past failures elsewhere have relevance to NZ• Unretrofitted URM buildings loaded to about 6 times their calculated capacity• Why did they not all completely collapse?
Short duration of ground shaking(Less than 10 seconds of string ground shaking on both occasions) 0.30Acceleration(g) N64E 0.15 0 -0.15 4 Sept 2010 -0.30 0 10 20 30 40 50 60 Time(s) 22 Feb 2011
Implications for elsewhere in NZ?• The URM building stock throughout NZ is remarkably homogeneous• The same outcome can be expected anywhere in NZ after a large earthquake1. Do nothing2. Seismic improvement3. Demolition
Von Sierakowski and Co. Building The Von Sierakowski Building, Corner Tuam and Columbo Street (1906). The factorywas erected in 1906 and was the largest wireworks factory in the Colonies.
Von Sierakowski and Co. Building [September 2010]The September Darfield earthquake of 2010 caused out-of-plane wall failure and lossof the parapet.
Von Sierakowski and Co. Building [February 2011]The September Darfield earthquake of 2010 caused out-of-plane wall failure and lossof the parapet.
The Christchurch Cathedral [February 2011]The Cathedral was designed by the Englishman G.G. Scott and work began on it in1863. The tower and spire, paid for by the Rhodes family, are complete in thephotograph but were damaged multiple times by earthquakes in 1881, 1888 whichbrought down part of the top section, and again in 1901.
Poor quality of mortar Many tested samples 1.0-1.5 MPaΤ=C+µN compression strength
Large vertical accelerations, short duration Τ=c+µN If c = 0 and N=0? Vertical accelerations high frequency
Timber frame with masonry veneer (18) Reinforced concrete Timber construction or steel structure (16) (20) URM stone (22) URM brick Approximately 250 (24) churches
Damage to rubble masonry Damage to brick masonry Damage to a gable in Stconstruction in Holy Trinity in St Luke’s church (1859), James church (1926),church (1872), Avonside Christchurch Riccarton Plaster Brick Unrein. (?) concrete Stone 10 220 170 230 St James Church (1926), Riccarton; wall composition
BasilicaDocumenting damageSystem identificationDamage detectionPerformance in aftershocks
Conclusions• URM – why was there not more collapses (because of low duration)?• Massive loss of architectural heritage “Christchurch now has no earthquake-prone buildings”• Clear lesson for all of NZ regarding earthquake prone buildings. Improve or remove• Better knowledge of URM and diaphragm materials• Proven success of a number of retrofit technologies• Good data on seismic performance macros URM building stock and of churches• RCM failures mostly attributable to poor grouting and rebar detailing
As the recovery begins ...• Futility is appearing, public lack of confidence• Insurance companies saying that they will not insure a strengthened URM building• Used to be 1/3rd of 0.22. Now 2/3rd of 0.30 (strengthening requirement is now 3 times what it was a year ago)• “Knock them all down – its too hard to make them safe”
“Is it acceptable that 2 New Zealand cities have been destroyed by earthquakes in the past 80 years?” Nigel Priestley at the PCEE conference